Color kinescope



the .given color will not remain in exact registration with-the COLOR KINESCOPE Rudolf C. Hergenrother, West Newton, Mass., assigner to Raytheon Manufacturing Company, Waltham, Mass., a corporation of Delaware Application May 2.5, 1954, Seriai No. 432,147

17 Claims. (Cl. 17S-5.4)

This invention relates to color kinescopes and, more particularly, relates to means for coordinating the position of an electron beam on the fluorescent screen `of a color kinescope and a corresponding color input signal.

One form of color kinescope now in use includes a uorescent screen carrying a plurality of vertically `disposed phosphor elements or strips. These phosphor strips are arranged in groups of three with each element of the group capable of emitting light of a different primary color when impinged upon by an electron beam. As the electron beams scans across the phosphor strips at :a substantially constant rate, determined by the parameters of the horizontal dellection circuit, the various phosphor strips iluoresce, respectively, in a color sequence such as red, green, and blue, or in any other sequence desired, depending upon the order of arrangement of the .phosphor elements of each group or triplet.

A plurality of trains of color video signals are derived from the color television receiver, each one representative .of the primary component colors of `the scene being televised. For example, in the usual tri-color system there lare three separate color video signals, -which are indicative of the red, green, and blue components, respectively, of the televised scene. The number vof ,separate color video signals corresponds to the number of phosphor elements in a group and the information .conveyed by each of the video signals corresponds to Ytheco1o12of light emitted by a corresponding phosphor strip in ,each group. 'Ihe relative yamplitudes of these color-.video signals are a function of the light intensity of the .respective component colors present in "the televised scene.

lIn this system each color video signal is .applied sequentially to the intensity control grid of the kinescope while the electron beam lis moving past the phosphor strip corresponding to that color. For example, V.the red video signal should be applied to the electron gunonly while the electron beam is traversing the red-lightemitl ting -phosphor strip on the uorescent screen. In order-to recurrently supply the separate color video signals oneat .a time and in a ,pre-determined sequence yto the intensity grid, a color coding device is used. Thetcolor coder is continuously supplied with the three separate color video signals and is adapted to permit the passage therethrough Vof .but one color signal at a time. The kinescope grid is thus cyclically receptive of a given color Video signal.

In the usual tri-color system, all three video signals are supplied to the kinescope grid during an interval ofitime substantially equal lto that taken for the electron beam to traverse each color triplet.

VIn. actual practice, the electron beam position during presence of video information corresponding Vto a appropriate phosphor strip of the uorescent screen because of such factors as irregularities in either the beam scanning rate or in disposition of the color triplets'on the fluorescent screen, or both.

The purpose of this invention is tovachieve the lref quired coordination between the position of the electron beam on the fluorescent screen and the receipt of corresponding color Video information. Means are provided for producing signals representative of the instantaneous position of the electron beam on the uorescent s*creen as the beam is scanned across the phosphor strips of the screen. These signals, which hereinafter will :be referred to as scan-register signals, are fed to the color coder. This color coder, which essentially is a gating circuit, is periodically receptive of the scanned register signals in addition to being continuously supplied with the three incoming color video signals; in response to the receipt of each incoming scan-register signal, the color coder gates the various color video signals to the intensity control grid of the electron gun.

The means for producing the scan-register signals i11- cludes an electron beam intercepting electrode, otherwise referred to as a scan-register grid, which includes a mul- "ice tiplicity of spaced, electrically interconnected elements,

referred to hereinafter as signal elements, which are spaced from the fluorescent screen which is covered with an electrically-conductive coating and biased negative with respect thereto. These signal elements may be ,in the form of wires or `strips which are aligned parallel to and in register with appropriate ones of the phosphor strips of said fluorescent screen. These signalgelements Lemit secondary electrons when impinged upon by a Vscanned electron beam and pulses of vvcurrent: flowing through an output circuit during the traversal of said beam past these elements provides scan-register signals.

By spacing the signal elements of the scan-,register grid V-has black areas therein, or areas in which a particular color is absent, the beam current becomes zero in .these areas and, if no special provision is made, no scan-.register signals will be produced in such areas. rEllis will-result in diticulties at the edges of dark areas since no 4scanregister signal will precede the transiti()n from a dark Larea to Aa light one. Furthermore, in areas of the Lpicture where the luminance is 10W, the beam Acurrent .may vbecome so small that the resulting low level of the seanregister signal will be inadequate vfor lirm control .of Ithe color coder. If, on the other hand, the electron beam ,is turned on in order to obtain the scan-register signal, a

a gratuitous excitation of the uorescent yscreenof vordinary color kinescopes would be produced.

These diiiiculties can be overcome by designing the ,color coder so that once during eachcoding cycle a xed reference potential or bias is appliedto the grid of the electron gun, which is independent of the presence or amplitude of the color signal or signals, and by'using a blank strip on the fluorescent screen :between each group of three color strips and positioned in alignment Vwith the signal elements of the scan-register grid. The proV- gramming sequence for the color coding is such that',

when the coder is triggered by a scan-register signal, it Will gate successively the red, green, and blue signals and then will set the beam at a certain reference level. The time intervals are arranged so that the color gating occurs when the beam is travers-ing the respective vcolor strips and the reference voltageis applied toV the `intensity control grid while the beam is passing across the blank strip. With this arrangement, the scan-register signals will be of substantially constant amplitude and will cause the color coder to function independently of the presence or amplitude of the color signal, while the presence of the blank strip will prevent the bias level beam current from producing undesired illumination of the fluorescent screen during the interval in which only a scan-register signal is derived.

Although the presence of the blank strip will lower the allowable duty cycle of the tluorescent strips and will cause these strips to be narrower than otherwise, at least part of the blank strip would have been shadowed by the scan-register grid elements in any event.

If the uorescent screen coating is maintained at a potential (relative to some fixed reference potential such Vas that of the cathode) which is several times that of the scan-register grid potential (relative to said reference potential) the electron beam will now be converged or focussed between each pair of signal elements of the 'scan-register grid by the accelerating electric lield between the lluorescent screen coating and the scan-register grid. In order to provide proper convergence upon the individual strips of a given color group, a grid wire or element will be required for each separate color phosphor strip. -If a blank strip is positioned between each group of three-color strips, there will be four grid wires or signal elements for each group of color strips. This means that four impulses will be produced for each group or triplet of color strips. lf these impulses are of equal amplitude, an ambiguity will result in the color coder concerning color selection. This ambiguity can be resolved if every fourth impulse is caused to have a different amplitude from that of the other three adjacent signals. This may be done either by making every fourth signal element larger than theadjacent ones, or

'byhaving all signal elements of the same size but with every fourth element coated with a material having a markedly. different secondary emission ratio than that of the adjacent elements. In either case the color coder programming sequence would be keyed by the large amplitude impulse which would serve as the scanregister signal.

Another scan-register grid may consist of a series of spaced strips `disposed in electrical `contact with the uorescentscreen coating and made of an electricallyconductive material having a secondary emission ratio considerably different from that of the material of the liuorescent screen coating. lf the coating is made sutilciently negative relative 'to the accelerating anode 0r aquadag, secondary emission of electrons from the scanregis'ter grid to the anode when the signal elements of the scan-register grid are struck by the electron beam will reach saturation. lf a constant current electron beam is scanned across the iluorescent screen, a pulsey of current will be produced whenever' the beam crosses one of the metal strips of the scan-register grid. These pulses which comprise the scan-register signals will be superimposed on the modulation produced by the color video signals when a color picture is being reproduced. By locating the signal elements of the scan-register grid opposite a blank strip on the fluorescent screen, in the manner already described, the color coding may be initiated without producing undesired illumination of the fluorescent screen during the actuation of saidcoder; moreover, the scan-register signals will be of constant amplitude and will cause the color coder to function independently of the presence or amplitude of the color video signals, provided, of course, that the video information and scan-register signals are first separated.

The principles of operation and the objects of this invention will be appreciated from a consideration of the drawing in which: Y p Fig. 1 illustrates an embodiment of the subject invention in which a single scan-register grid element is used for each color group;

Fig. 2 is a fragmentary view showing in detail the relation between the scan-register grid and the fluorescent screen;

Figs. 3 and 4 illustrate modifications of the scan-register grid of Figs. l and 2 used in applications involving post-deliection focussing;

Fig. 5 is a view illustrating a modiiication of the tubo and output circuitry of the embodiment of Fig. l; and

Fig. 6 is a detailed view showing the relationship between the scan-register -grid elements and the target electrode.

Referring to Fig. l, the cathode ray tube 12 is shown which includes an electron gun 14 comprising a cathode 15, electron beam intensity control grid 16, focussing and accelerating anode 17 and an accelerating anode 18- which may consist of an electrically-conductive coating on the inner wall of the tube envelope. Tube 12 also iu-I cludes horizontal and vertical deilection coils 11 receptive of signals from appropriate horizontal and vertical de-i ilection circuits 13.

Mounted near the viewing face 19 of tube 12 is a target electrode 20 which includes a rigid supportingi member 22 which may be made of glass mica, or any' other material capable of transmitting light, a uorescent screen 23 and an electrically-conductive, electronpermeable layer or coating 27 on said fluorescent screen. The uorescent screen may, in some cases, be deposited directly upon the viewing face of the tube; in this case the supporting member 22 may be eliminated. The

thickness of the layers 23 and 27 of the target electrode 20 is greatly exaggerated in the interest ofclarity of illustration.

Coating 27 preferably is made of aluminum which may be applied by a process of evaporation under a vacuum. Coating 27 serves as an electrode to which one terminal of a high-voltage source 29 may be connected. The anode 18 and coating 27 are maintained at lthe same lhigh potential iu order to prevent flow of secondary electrons from the fluorescent screen coating to the Fluorescent screen 23 consists ofY a pluralityrof group or triplets of vertically-disposed phosphor strips or areas 24 capable of emitting red, green, and blue light, respectively, as indicated by the cross-hatching whenever an electron beam impinges thereupon. The groups of phosphor strips are repetitively arranged over the ltarget area with the strips preferably normal to the direction of line scanning in order to obtain the maximum resolving power. The electron beam may be permitted to scan the phosphor strips at an angle other than degrees provided that reduced resolving power may be tolerated. Since line scanning is horizontal in television systems now in general use, the phosphor strips preferably are arranged vertically.

Spaced between adjacent groups or triplets of the fluorescent screen isan elongated blank strip or area 2S which either is uncoated or contains a deposited material which does not phosphoresce in the visible spectrum. The elongated regions lying between color trip- Alets will be referred to in the specication 'and claims Aeither as blank strips or blank areas. Although the groups of color strips so far described have been Atertiary groups comprising the. colors red, green, and blue, it should be understood that this invention is not so limited. The number of phosphor strips and the color emission thereof will-depend upon the number of primary component colors selected for .the television system being considered.

A scan-register grid -30 is spaced from the iluorescent Vscreen and comprises a plurality of spacedsignal ele- 7 4emission ratio of the lluorescent screen coating, the current 'is correspondingly greater or smaller when the beam ,impinges' on one of the signal elements 60 than when the AAbeam strikes viluorescent screen'27.v The scan-register -signalsmay be lcapacitively coupled to the color coder circuitry by means of capacitor 68. .The scan-register signals may be separated from the videov information on the basis of amplitude. An amplitude sensitivetra'nslation device, such as an ampliiier biased well below cut-oli, may-be inserted between the voutput terminal 7 0 of the tube and the color coder so that only the higher amplitude scan-register signals may be transmitted. YThis invention is not limited to the particular details of construction, materials and processes described, as many 4equivalents will suggest themselves to those skilled in the fart. It is, accordingly, desired that the appended claims Vbe given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

l. In combination, a cathode ray tube adapted to re- 'ceive video information corresponding to the presence .of primary component colors in a televised scene and including means for producing an electron beam, a lluores- 'cent screen composed of a plurality of recurrent groups Yof elongated phosphor areas extending along said screen 'in la given direction and a plurality of blank areas positioned between adjacent ones of said groups, each of said phosphor areas of a given group beingproductive of light lof `a different primary colorV when interceptive of said electron beam, a beam intercepting grid positioned ad- V'jacentsaid fluorescent screen and including a series of spaced signal elements arranged parallel to and in alignment with corresponding blank areas, deflection means for scanning said beam along said liuorescent screen in Aadirection substantially normal to said given direction, and means responsive only to the interception of said electron beam by said signal elements for producing control signals independently of the presence of said video information. Y

2. In'combination, a cathode ray tube adapted to receive video information corresponding to the presence of 'plimary component colors in a televised scene and including means for producing an electron beam, a uorescent screen composed of a plurality of recurrent groups of elongated phosphor areas extending along said screen in a given direction and a plurality of blank areas positioned between adjacent ones of said groups, each of said phosphor areas of a given group being productive of light 'of a different primary color when interceptive of said felectron beam, a beam intercepting grid positioned adjacent said iluorescent screen and including a series of spaced signal elements arranged parallel to and in alignment with corresponding blank areas, deection means for scanning said beam along said uorescent screen in a direction substantially normal to said given direction, means responsive only to the interception of said electron beam by said signal elements for producing control signals independently of the presence of said video information, and coding means triggered into operation solely by said vcontrol signals for modulating said electron beam with 'video information concerning a given primary component color in synchronism with the traversal by said beam of a phosphor area corresponding to that primary component color.

3. In combination, a cathode ray tube adapted to receive video information corresponding to the presence of primary component colors in a televised scene and including means for producing an electron beam, a fluorescent screen composed of a plurality of recurrent groups of elongated phosphor areas extending along said screen in a given direction and a plurality of blank areas positioned between adjacent ones of said groups, each of said phosphor areas of a given group being productive ofllight of a diierent primary color when interceptive of said electron beam, a beam intercepting grid positioned adjacent said uorescent screen and including a series of spaced signal 'elements arranged parallel to and in alignment with corresponding blank areas, deflection means for scanning said beam along said uorescent screen in a direction substantially normal to said given direction, and means including said beam intercepting grid for deriv- -ing control signals only during the traversal of said electronb'eam across, said blank areas independently of said video infomation..

4. In' combination, a cathode ray tube adapted to receive video information corresponding to the presence of primary component colors in a televised scene and including means for producing an electron beam, a liuorescent screen composed of a plurality of recurrent groups of elongated phosphor areas extending along said screen in a given direction and a plurality of blank areas positioned between adjacent ones of said groups, each of said phosphor areas of a given group being productive of light of a dilerent primary color when interceptive of said electron beam, a beam intercepting grid positioned adjacent said uorescent screen and including a series of spaced signal elements arranged parallel to and in alignment with corresponding blank areas, deiiection means for scanning said beam along said fluorescent screen in a direction substantially normal to said given direction, means including said beam intercepting grid for deriving control signals only during the traversal of said electron beam across said blank areas, and coding means triggered into operation solely by said control signals for modulating said electron beam with video information concerning a given primary component color in synchronism with the traversal by said beam of a phosphor area correspondingto that primary component color, said coding means further permitting derivation of a xed potential during the traversal of said beam past said blank areas.

v 5. In combination, a cathode ray tube adapted to receive video information corresponding to the presence of primary component colors in a televised scene and including means for producing an electron beam, a fluorescent screen composed of a plurality of recurrent groups of elongated phosphor areas extending along said screen in a given direction and a plurality of blank areas positioned between adjacent ones of said groups, each of said phosphor areas of a given group being productive of light of a dierent primary color when interceptive of said electron beam, a beam intercepting grip spaced from said fluorescent screen and including a series of spaced signal elements arranged parallel to and in alignment with corresponding blank areas, deflection means for scanning said beam along said uorescent screen in a direction substantially normal to said given direction, and means j responsive only to the interception of said electron beam by said signal elements for producing control signals independently of the presence of said video information.

6. In combination, a cathode ray tube adapted to receive video information corresponding to the presence of primary component colors in a televised scene and including means for producing an electron beam, a uorescent screen composed of a plurality of recurrent groups of elongated phosphor areas extending along said screen in a given direction and a plurality of blank areas positioned between adjacent ones of said groups, each of said phosphor areas of a given group being productive of light of a different primary color when interceptive of said electron beam, a beam intercepting grid spaced from said fluorescent screen and including a series of spaced signal elements arranged parallel to and in alignment with corresponding blank areas, deflection means for scanning said beam along said fluorescent screen in a direction substantially normal to said given direction, means responsive only to the interception of said electron beam by said signal elements for producing control signals independently of the presence of said video informa- 4tion, and coding means triggered into operation by said control signals .for .modulating said electron fb'eamwith video information concerning a-fgiyen primary component color in synchronisnr .with .the traversal by said be'am' of -a :phosphor area corresponding to .that primary component color.

7. ln combination, a cathoderay' tube including .means for producing an :electron beam, a `uorescent screen 1includinga rpluralityof recurrent .groups yof*elonfga'ted-'phosphor areas extending along. said 'screen-in a .give'ndirec- 7tion and a;plurality-of elongated blank areas positioned between adjacent 'ones of said groups, each of said phosphor areas of :a :given group beingproduetive of light 'of .a different primary color when-interceptive of said electron beam, an electron-.permeable electrically :conductivev layer disposed in Contact with 'said 'uorescent screen, .a beam lintercept-ing fgrid electrically insulated from said -luorescent lscreen and including a multiplicity :ot` spaced signal elements arranged parallel to and in alignment with corresponding blank Aareas and 'capable of emitting secondary electrons when impinged upon by :said lelect-ron beam, rncansi'or maintaining, 'said'. grid negativewith fre- Vspeet to said layer, 4deflection means -for recurrentlyscanning said beam along said fluorescent screen rin 'a direction substantially normal to' said given direction, means respons-ive'only to the interception `of said beam `"by "said i signalelements for .producing control signals, means Vfor .generating video signals corresponding to cachot said primary colors, a source of fixed potential, and coding :mea-ns triggered into operation by said control signals for modulating the intensity'of said beam kduring the traversal of said beam A:past av phosphor area of a given primary color in laccordance with a video signal vrepresentative -of information concerning that `primary color.

8'. ln combination, a cathode ray-tubeincluding means for producing al1-electron beam, an `electron beamintensity control electrode, a iluorescent screen including a plurality of recurrent groups Jof elongated phosphor areas vextending along said screen' in a given direction and a .plurality of elongated blank areas .positioned between -'adjacent ones of said groups, each of said .phosphor areas of a given group being productive "of light of a different primary color when interceptive of `said electron beam, an' electron-,permeable electrically conductiveV layer ydisposed in Contact with said fluorescent screen, la beam .intercepting grid positioned adjacent saidiluorescent'screen and including `a multplicity'of spaced signalelernents 'arranged parallel to and in alignment with corresponding blank areasiand capable `of emitting secondary electrons when impin'ged Aupon by said electron beam, deflection :means for re'currently scanning said beam along said fluorescent screen in adirection substantially `normall to said ,-.give'n direction, means responsive Aonly to the `interception of said beam by said signal elements orproleucing cont-rol signals, means for genertingvideosignals corresponding to each of said primary colors, a source of fixed potential, and coding means triggered 'into'open ation by said control signals for modulating the intensity of said beam during the 'traversal of said beams past-a .phosphor area of a given primary color Yin `accordance with a video signalrepresentative of information conce-rning that primary color, said coding means -further permitting vapplication of said fixed potential to said -intensity control electrode during the traversal of said beam past said blank' areas.

9. In combination, a cathode -ray tube including V-Irleans for producing' an electron beam, an electron beam intensity control electrode, -a iiuorescent screen including a plurality of recurrent groups of elongated phosphor areas extending along said screen in -a given kdirection and a plurality of elongated blank areas positioned between a'djacent ones of :said groups, each of said phosphor areas of a 'givengroup being productive of .light Vof a l'di'erent pri-mary color when interceptive of said electron beam,an electron permeable electrically `conductive layer disposed in Contact with said -uorescent screen, abeam intercepterroneos ing'grid positioned in contact with said layei-'f'and includ .ing multiplicity 'of spaced :signal elements arranged Vparallel :to and iin alignment with corresponding blank TareasV fand capable of emitt g secondary electrons when `impin'gfed' upon 'by said elec'tro'n lbea'rn, Vdeflect-loirrirearis `tor"recinrently scairningfs-ad beam :along 'said fluorescent screen :in adirection substantially normal Vto said given fd'ireotion, means r'e'spons'ive only to l'the inte'rc'e'ptio'rl VVif said beam by 'said Asignal elements for producing control signalsfmeans for (generating video signals corresponding to eachof said primaryolor's, a source oi-Xetl'pot'tial, and codngmeans triggered into operation b'ysaid control signals :for modulating the intensity of said-beam during Ythe' traversal Tof said beam `past a phosphor a-'r'ea of a .'givenfprimaryfcolor inV accordance with a video signal representative of information concerning that 'primary color, said coding means further permitting application of said .iixe'd potential' 'to said `intensity control electrode during `the traversaliot' Said beam past said blankfare'as.

l0. iin :combination .a cathode ray 'tube 'adapted VVAto refceive video information 'corresponding to the presence -ot primary component colors in a televised 'scene and .including means forpro'du'cing an electron' beam, aores- .'cent screen composed oli `a plurali-ty of recurrent groups :of elongated :phosphor areas extending along said sci-een in a :given fdirection `andV a plurality of 'blank' Vareas `positioned'between'adjacent onesjof said groups, 'cachot 'said phosphor areas of a given 'group being 'produet'ive'of light of a' dillerent primary :color when interceptive 'of said `electron beam, `a beam intercepting grid positioned adi -jacentsaid'fluorescent screen :and sp'a'ce'd therefrom, means tor producing ansfaccelerating'eld in the "region of said beam .intercepting'Igridwhereby safid beamvvis focussed -on said iluorescent screen, .said fgri'd' .including a 4se of fspacedelements `eachfin'.alignment with the'boundai'y df -two adjacent areas yof .the luo'rescent screen, deflection means for -recurrently :scanning `said beam a'l'o'ng said -uorescentscreen1.in.a direction substantially ynorinal to said given direction, and means .responsive only to the interception 'of said 'electron beam by these 'of'said ele'- ments .lying adjacent the boundary `of a gi've'n blank aree. -and the phosphor area .immediately preceding 'said given blank area forrderiving'fcontrol signals independently of the presence `of said video information.

11. `In combination a cathode ray tube adapted to 're- -ceive kvideo Ainformation corresponding 'to the .presence of primary "component `colors ina ltelevised scene and 1in- 'clu'ding means for .producing .an electron beam,- a llu'orescent screen lcorr'lposed Aof a plurality of recurrent l"grot'lps of Yelongated'phosphor areas extending along said screen in-'fa givenadirection and aplurality of 'blank areas posi'- tioned between adjacent ones'of said groups, each of 'said phosphor Yareas of agivenfgroup being productive oflfig-ht Aof a different primary color when intercepti've of said electron beam, a beam 'intercepting grid positioned 'adjacent'saiduorescentscreen and spaced therefrom, fr'nean's for produc' g anfacceleratingi'eld in the region `of s'aid Heanriintercepnng grid where-by said beam is focussed on said uoresc'ent screen, said grid including a series of spaced elements each in alignment with the boundary of two adjacent areas of the iluorescent screen, dellection means for .recurrently scanning said beam along said iluores'cent screen in `a direction substa'nt'i'ally normal to said given "direction, lmeans responsive only to the interception of said electron beam by those of lsai-d elements lying opposite the boundary of a given blank area Aand the phosphor area immediately preceding said, given blank area Vfor deriving `control signals independently of the presence of'sai-d video information, and coding. means 'triggeredfinto operation by said control signals for modulating-'said electron 4beam 'with video information concerningafgiven primary component col'or in synchronism with Ithetravfe's'al bysaid beam of a phosphor areacorrespending-:to that primary component color, said coding Ameans further permitting derivation` of a tixed potential during the traversal of said beam past said blank areas.

12. In combination a cathode ray tube adapted to receive video information corresponding to the presence of primary component colors in a televised scene and including means for producing an electron beam, a lluorescent screen composed of a plurality of recurrent groups of elongated phosphor areas extending along said screen in a given direction and a plurality of blank areas positioned between adjacent ones of said groups, each of saidY phosphor areas of a given group being productive of light of a different primary color when interceptive of said electron beam, a beam intercepting grid positioned adjacent said uorescent screen and spaced therefrom, means for producing an accelerating field in the region of said beam intercepting grid whereby said beam is focussed on said uorescent screen, said grid including a series of spaced elements each in alignment with the boundary of two adjacent areas of the uorescent screen, those of said .elements lying adjacent the boundary of a blank area and the phosphor area immediately preceding this blank area being of larger size than the remaining elements, deec- ,tion means for recurrently scanning said beam along said uorescent screen in a direction substantially normal to said given direction, and means responsive only to the interception of said electron beam by those of said elements of larger size for deriving control signals independently of the presence of said video information.

13. In combination a cathode ray tube adapted to receive video information corresponding to the presence of primary component colors in a televised scene and including means for producing an electron beam, a lluorescent screen composed of a plurality of recurrent groups of elongated phosphor areas extending along said screen in a given direction and a plurality of blank areas positioned between adjacent ones of said groups, each of said phosphor areas of a given group being productive of light of a different primary color when interceptive of said electron beam, a beam intercepting grid positioned adjacent said uorescent screen and spaced therefrom, means for producing an accelerating eld in the region of said beam intercepting grid whereby said beam is focussed on said uorescent screen, said grid including a series of spaced elements each in alignment with the boundary ofv two adjacent areas of the fluorescent screen, those of said elements lying opposite the boundary of a blank area and the phosphor area immediately preceding this blank area being of larger size than the remaining elements, deflection means for recurrently scanning said beam along said fluorescent screen in a direction substantially normal to said given direction, means responsive only to the 'inter- Vception of said electron beam by those of said elements of larger size for Ideriving control signals independently of the presence of said video information, and coding means triggered into operation by said control signals for modulating said electron beam with video information concerning a given primary component color in synchronism with the traversal by said beam of a phosphor area corresponding to that primary component color, said coding means further permitting derivation of a fixed potential yduring the traversalof said beam past said blank areas. a

14. ln combination a cathode ray tube adapted to receive video information corresponding tothe presence of primary component colors in a televised scene and including means for producing an electron beam, a fluorescent screen composed of a plurality of recurrent groups of elongated phosphor areas extending along said screen in a given direction and a plurality of blank areas positioned between adjacent ones of said groups, each of said phos- F phor arcasv of a given group being productive of light of a different primary color when interceptive of said electron beam, a beam intercepting grid positioned adjacent said uorescent screen and spaced therefrom, means for producing anaccelerating field in the region of said beam jacent areas of said tluorescent screen, those of said elements lying adjacent the boundary of a given blank area and the phosphor'area immediately preceding said given -blank area having a greater secondary emission ratio than the remaining elements, deflection means for recurrently -scanning said beam along said uorescent screen in a direction substantially normal to said given direction, and means responsive only to the interception of said electron beam by those of said elements of greater secondary emission ratio for deriving control signals independently of the presence of said video information.

15. In combination a cathode ray tube adapted to receive video information corresponding to the presence of primary component colors in a televised scene and including means for producing an electron beam, a tluorescent screen composed of a plurality of recurrent groups of elongated phosphor areas extending along said screen in a given direction and a plurality of blank areas positioned between adjacent ones of said groups, each of said phosphor areas of a given group being productive of light of a different primary color when interceptive of said electron beam, a beam intercepting grid positioned adjacent said iluorescent screen and spaced therefrom, means for producing an accelerating field in the region of said beam intercepting grid whereby said beam is focussed on said fluorescent screen, said grid including a series of spaced elements each in alignment with the boundary of two adjacent areas of said fluorescent screen, those of said elements lying adjacent the boundary of a given blank area and the phosphor area immediately preceding said given blank area having a greater secondary emission ratio than the remaining elements, deection means for recurrently scanning said beam along said fluorescent screen in a direction substantially normal to said given direction, means responsive only to the interception of said electron beam by those of said elements of greater secondary emission ratio for deriving control signals independently of the presence of said video information, and coding means triggered into operation by said control signals for modulating said electron beam with video information concerning a given primary component color in synchronism with the traversal by said beam of a phosphor area corresponding to that primary component color, said coding means further permitting derivation of a fixed potential during the traversal of said beam past said blank areas.

16. In combination a cathode ray tube adapted to receive video information corresponding to the presence of primary component colors in a televised scene and including means for producing an electron beam, a fluorescent screen composed of a plurality of recurrent groups of parallel elongated phosphor strips extending along said screen in a given direction and a plurality of blank strips positioned between adjacent ones of said groups and parallel to `said phosphor strips, each of said phosphor strips of a given group being productive of light of a diterent primary color when interceptive of said electron beam, a beam intercepting grid positioned adjacent said fluorescent screen and spaced therefrom, means for producing an accelerating field in the region of said beam intercepting grid whereby said beam is focussed on said uorescent screen, said grid including a series of spaced elements one foreach strip of said uorescent screen, those of said elements cooperating with said blank areas having a greater secondary emission ratio than the rcmaining elements, deflection means for recurrently-scanning said beam along said uorescent screen in a direction substantially normal to said given direction, and means responsive only to the interception of said electron beam by those of said elements of greater secondary emission ratio for deriving control signals independently of the presence ofsaid video information. A j

V17. In combination'a cathode ray tube-adapted to receive video information corresponding to the presence of primary component colors in a televised scene and including means for producing an electron beam, a fluorescent screen composed of a plurality of recurrent groups of parallel elongated phosphor strips extending along said screen in a given direction and a plurality of blank strips positioned between adjacent ones of said groups and parallel to said phosphor strips, each of said phosphor strips of a given group being productive of light'of a 'dilerent primary color when interceptive of said electron beam, a beam intercepting grid positioned adjacent said fluorescent screen and spaced therefrom, means for producing an accelerating field in the region of said beam intercepting grid whereby said beam is focussed on said Vfluorescent screen, said grid including a series of spaced elements one for each strip of said fluorescent screen, those of said elements cooperating with said blank strips having a greater secondary emission ratio than the remaining elements, decction means for recurrently scanning said beam along said lluorescent screen in a direction substantially normal to said given direction, means responsive only to the interception of said electron beam by those of said elements of greater secondary emission ratio for Ideriving control signals independently of the presence of said video information, and coding means triggered into operation by said control signals for modulating said electron beam with video information concerning a given primary component color in synchronism with the traversal by said beam of a phosphor strip corresponding to that primary component color, said coding means further permitting derivation of a xed potential during the traversal `of said beam past said blank areas, said coding means further permitting derivation of a fixed potential during the traversal of said beam past said blank strips.

References Cited in the le of this patent U'NlTED STATES PATENTS 2,648,722 Bradley Aug. 11, 1953 2,669,675 Lawrence Feb. 16, 1954 20 2,674,651 Creamer Apr. 6, 1954 

